PERSPIRATION AND RESPIRATION. 239 
furnish a uniform portion of the air inside and outside of the apparatus for ex- 
amination, so long as the air current is in motion—that is, so long, in general, as 
an experiment continues.* 
In closing I take the liberty to call attention specially to the fact that the 
respiratory and perspiratory apparatus in the Physiological Institute here is the 
first in which a result is possible under normal conditions; persons can live in 
it just as in a well-aired room, in which they can freely move, labor, eat and 
sleep, as they had been accustomed to do. By a movable window at the door of 
the saloon, food and other things can be taken in and out, without the fear of 
disturbing the experiment, with just as little concern as in a room, supposing 
the chimney-draught in order, one opens the door to stir the fire or remove the 
ashes without the escape of smoke. 
The person outside of the saloon, conducting the experiment, does not in the 
least disturb the result by his respiration, &c., for the amount of carbonic acid 
of the air entering the saloon is constantly controlled by one of the two exam- 
ining apparatus, and can therefore be drawn off. I have never hesitated to 
smoke cigars during the progress of a test experiment, or to receive visitors 
who also smoked, knowing that the changes of the air outside of the saloon 
are to be ascertained precisely in the same way and with the same exactness 
as those in the saloon. As only the difference is calculated, it is all the same 
whether this is more or less, provided it can be determined with certainty. 
In the test experiment with candles I have hitherto employed a change of 
air of somewhat more than eleven English cubic feet (about 314 litres) per 
minute. In an hour, therefore, there entered into the saloon, which contains 
somewhat more than 12,000 litres, much more than its own capacity of fresh air. 
By increasing the force of the suction-pumps which are worked by the engine, 
the air-change can be quadrupled without thereby producing the slightest sensi- 
ble draught in the saloon, except in the immediate vicinity (four to six inches) of 
the openings in the saloon door. Opposite to these openings the transverse sec- 
tion of the saloon is so considerable, that the rapidity of the movement of the 
air must become imperceptible in the saloon itself, even if it is felt immediately 
at the narrow openings. Under the greatest force of the suction-pumps, which 
answers to a ventilation of 3,000 English cubic feet an hour, a candle still burns 
perfectly undisturbed in the middle of the saloon. 
That the rapidity of the entrance of the air at the saloon door is greater than 
that of its diffusion—in other words, that there is no loss of carbonic acid to 
be feared from the diffusion—is established simply by noticing whether the 
pungent smelling smoke generated and observed in the saloon is observable at 
the cracks on the outside. After this experiment had been repeatedly made 
with negative results, one might have been @ priori, satisfied that no carbonic 
acid developed in the saloon can be lost, which fact is also perfectly established 
by the quantitative determinations. I am convinced that with this apparatus 
all questions of animal and vegetable physiology, so far as they relate to an in- 
erease or diminution of carbonic acid and water in the air, can be solved with 
exactness and under perfectly natural conditions.t 
Nore BY THE TRANSLATOR.—Professor Pettenkofer handed me the above report, at my 
request, when I once visited him during an experiment in the Physiological Institute, and 
be then made in pencil-mark the several short notes which are given in connexion with the 
translation. A. TB 
* The test experiments with candles have since been extended to twelve hours, and have 
given an entirely accurate result. As already stated, the pump apparatus connected with 
the propelling machinery provides, at present, for the examination of the two portions of air, 
( Luftproben.) 
tThese anticipations have all been entirely realized, since November, 1860, by experi- 
ments, as well upon men as upon animals, 
